Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $238.63   9.521%   $261.35   $261.35   $261.35   $261.40  
  Purchase #2 $137.74   4.319%   $143.689   $143.69   $143.70   $143.70  
  Purchase #3 $225.51   5.288%   $237.435   $237.44   $237.45   $237.40  
  Purchase #4 $149.35   13.386%   $169.342   $169.34   $169.35   $169.30  
  Purchase #5 $86.80   3.123%   $89.5108   $89.51   $89.50   $89.50  
  Purchase #6 $181.68   12.579%   $204.5335   $204.53   $204.55   $204.50  
  Purchase #7 $243.78   5.746%   $257.7876   $257.79   $257.80   $257.80  
  7 purchase totals = $1,263.49       $1,363.6479   $1,363.65   $1,363.70   $1,363.60